Organic Orbital Theory-Discovery of New Concepts in Basic Organic Chemistry.

已完成以下三个项目1.与传统的π-面非晶面选择过渡态模型(Felkin-Anh和Cieplak模型)不同的是，从理论上证明了π-面非晶面选择过渡态的反周面效应并不是决定面孔非晶面选择的必要条件。基于Salem-Klopman方程和前线轨道理论，提出了一种新的预测π面非对映选择的量子化学模型。该模型，即外前线轨道延伸模型(EFOE模型)对于预测大多数环酮氢化物还原的面状非对映选择性是非常有效的。有机体系和蛋白质中弱相互作用的定量分析.利用硒核自旋(1/2)的特性，弱…的性质和强度16族元素氢键中的更多相互作用(X…H-Y(X=O，S，Se，Te和Y=O，C)和Se…研究了Z(Z=N，O，F)非键吸引相互作用。结果表明，在这些情况下，相互作用不是静电的，而主要是施主-受主类型的轨道相互作用。在一个相关的项目中，我们检测到并表征了蛋白质中新型的弱原子相互作用，如C-S…O，S-S…O和C=O…这些相互作用主要是给体-受体类型，成键方向性较强。基础有机化学中问题的再探讨尽管氟苯在亲电取代反应中比苯更具活性，但人们普遍认为卤代苯是由于卤素的吸电子性质而失活的。定量分析了卤代苯中π-体系的轨道相互作用，得出结论：单取代苯的反应活性取决于最低占据的π轨道(π1)的能级，而不是前线轨道(π2或π3)的能级。因此，卤苯(氯、溴、碘)由于其电子捐赠性质而失活。用自然键轨道(NBO)分析研究了顺式效应和顺式效应问题。较少

The following three projects have been completed.1. New Theoretical Model for the Prediction of π-Facial Diastereoselection.Contrary to the claim of the conventional transition state models of π-facial diastereoselection (Felkin-Anh and Cieplak models), it is theoretically proven that the antiperiplanar effects involving the incipient bond in the transition state of nucleophilic carbonyl addition are not essential to dictate facial diastereoselection. Based on the Salem-Klopman equation and the frontier orbital theory, a new quantum chemical model for the prediction of π-facial diastereoselection has been proposed. This model, the exterior frontier orbital extension model (the EFOE Model) is found to be very effective for the prediction of facial diastereoselection of the hydride reduction of most cyclic ketones.2. Quantitative Analysis of Weak Interaction in Organic Systems and Proteins.Utilizing the specific property of selenium nuclear spin (1/2), the nature and the strength of weak … More interactions in hydrogen bonds involving Group 16 elements (X…H-Y (X=O, S, Se, Te and Y=O, C) ) and Se…Z (Z=N, O, F) non-bonded attractive interactions have been investigated. It is concluded that in all these cases the interactions are not electrostatic, but largely the donor-acceptor type orbital interaction. In a related project, we have detected and characterized new type of weak atomic interactions in proteins, such as C-S…O, S-S…O and C=O…S.These interactions are mainly the donor-acceptor type with strong bonding directionality.3. Reinvestigation of the Problems in Basic Organic ChemistryIt is generally accepted that halobenzenes are deactivated because of e-withdrawing nature of halogens, in spite of the fact that fluorobenzene is more reactive than benzene in electrophilic substittution. Quantitative analysis of orbital interactions of the π-systems in halobenzenes, it is concluded that the reactivity of mono-substittuted benzenes are dependent on the energy level of the lowest occupied π-orbital (π1) and not of the frontier orbitals (π2 or π3). Halobenzenes (Cl, Br, I) are therefore deactivated because of their e-donating property. The problems of cis-effect and gaucheeffect have also been investigated by natural bond orbital (NBO) analysis. Less